Various abbreviations that appear in the specification and/or in the drawing figures are defined as below:
ATSC Advanced Television System Committee
BS Base Station
BPSK Binary Phase Shift Keying
CA Carrier Aggregation
CP Cyclic Prefix
CR Cognitive Radio
CDMA Code Division Multiple Access
DTV Digital Television
DFT Discrete Fourier Transform
eNB evolved Node B
FFT Fast Fourier Transform
ISDB Integrated Services Digital Broadcasting
OFDM Orthogonal Frequency Division Multiplexing
PSD Power Spectral Density
QP Quiet Period
QPSK Quadrature Phase Shift Keying
RSRP Reference Signal Receiving Power
RSRQ Reference Signal Receiving Quality
SQPSK Staggered Quadrature Phase-Shift Keying
TVWS TV White Spaces
UE User Equipment
VSB Vestigial Side Band
WLAN Wireless Local Network
WiFi Wireless Fidelity
WiMax Worldwide Interoperability for Microwave Access
An LTE system has been accepted as a world-wide standard for wireless communications and it has capabilities of a peak download data rate of 1 Gbps, wide transmission bandwidth, low C-plane latency, increased user throughput and spectrum flexibility or the like. However, the LTE system also suffers from a bandwidth scarcity problem which has been very common in wireless communications. To alleviate this problem and boost spectrum efficiency, a CR technique has evoked considerable research interests lately because it is capable of efficiently utilizing unused “spectrum holes” on unlicensed bands without causing severe interference to primary users. Meanwhile, a CA technique is being standardized in the 3GPP as part of the LTE Release 10, which allows for aggregating non-contiguous spectrum fragments across multiple carriers. Therefore, incorporating CR features into the LTE system with the CA technique has become an efficient solution for solving the above spectrum scarcity problem.
Many researches with respect to the CR technique have been focusing on the TVWS. The database approach for TVWS access is considered as a tool to find available spectrum bands, which requires less investment other than an incumbent database that maintains data about used frequencies in the TV band. As compared to the database approach, spectrum sensing has its own advantages in respect of detecting more access opportunities for secondary systems working under a primary system. Besides, the database approach is always based upon coarse-grained allocation techniques and thus inferior to the spectrum sensing in determining whether a given channel is actually available. Furthermore, the spectrum sensing could be used to update and improve the database as appropriate.
In the CR-enabled networks, reliably obtaining available spectrum holes by the spectrum sensing (working independently or assisting the database) is crucial for secondary systems to access unlicensed bands opportunistically. As specified in IEEE 802.22 standard “IEEE P802.22™/D0.1, “Draft Standard for Wireless Regional Area Networks Part 22: Cognitive Wireless RAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Policies and procedures for operation in the TV Bands,” which is incorporated herein by reference in its entirety, out-of-band spectrum sensing refers to the case when an incumbent sensing activity is carried out in those channels other than working channels, aiming at obtaining available spectrum resource. This does not need a network level QP, and is a similar procedure to an inter-frequency measurement in LTE systems.
As specified in TS 36.3313GPP V10.3.0 (2011-09) Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC) (Release 10), which is also incorporated herein by reference in its entirety, a UE can be requested to perform intra-frequency, inter-frequency or inter-RAT measurements, and the measurement configuration includes the following parameters: measurement objects, reporting configurations, measurement identities, quantity configurations, and measurement gaps. According to different measurement purposes, the criteria for triggering the UE to send a measurement report are different. For instance, if the trigger type is set to event, Events A1/2 are for serving cell measurements, Events A3/4/5/6 are for intra/inter-frequency measurements and CA, as well as Event B1/2 are for inter-RAT measurements. However, in a cognitive LTE network, the conventional inter-frequency measurements cannot enable out-of-band spectrum sensing. This is because the measurement quantity of conventional inter-frequency measurement is RSRP/RSRQ in neighbor cells, and the decision condition is always dependent on whether the quality of a neighbor cell is better than a predetermined threshold. However, for the out-of-band spectrum sensing, the sensing target is the energy or feature of a received signal on an unlicensed band, where there may not be any reference signals like those transmitted in the LTE system. Therefore, the out-of-band spectrum sensing cannot be exploited simply by reusing the current measurement configuration in the LTE system, and new measurement configurations should be developed for cognitive radio based LTE systems
In view of the above, it would be desirable to configure out-of-band sensing in a cognitive LTE network without significant changes to the existing LTE architecture and spectrum efficiency could be improved by such out-of-band sensing. Further, the out-of-band sensing would not bring about interference to the primary or secondary system.